1. Field of the Invention
The present invention generally relates to mask pattern data processing methods, processing programs, and processing systems for use in forming mask patterns, and particularly relates to a method, program, and system for performing optical proximity effect correction.
2. Description of the Related Art
In the manufacturing of semiconductor devise, a light transfer device is used to print the pattern shape of a mask pattern on a wafer. As the patterns of semiconductor devices are made increasingly finer, optical proximity effect may cause adjacent patterns to come in contact with each other, may cause a pattern to have rounded corners, or may cause lines to be broken due to thinning. In consideration of this, a correction process may be performed to form a pattern shape exactly as desired on a wafer by processing pattern data such as to cancel or alleviate deformation based on the estimation of anticipated pattern deformation. This process is referred to as an optical proximity effect correction (hereinafter referred to as optical proximity correction).
Optical proximity correction (OPC) generates an auxiliary pattern associated with mask pattern data in order to correct a pattern on a reticle to attain a desired on-wafer image. In related-art pattern correction methods, generally, rules are defied for patterns for use in correcting design data. Based on the rules of correction pattern generation, a correction pattern is generated with respect to design data or with respect to reticle pattern data.
FIG. 1 is a drawing showing an outline of an optical proximity correction process.
In FIG. 1, a process flow shown on the left-hand side of the drawing serves to generate an auxiliary pattern with respect to reticle pattern data. A process flow shown on the right-hand side of the drawing serves to generate an auxiliary pattern with respect to design data.
When an auxiliary pattern is to be generated with respect to reticle pattern data, reticle pattern data is generated at step ST1A by converting design data based on conversion information such as information indicative of a layer in which the pattern is located and sizing information about the size of the pattern. In this manner, reticle pattern data 11 is produced from CAD data 10 that is created by the design staff.
At step ST2A, optical proximity correction is applied to the reticle pattern data based on correction information, which includes optical proximity effect correction values indicative of the range affected by optical proximity effect, and defines the rules of optical proximity effect correction. In this manner, corrected reticle pattern data 12 is derived from the reticle pattern data 11. Image is drawn based on the corrected reticle pattern data 12, thereby generating a tangible reticle 15.
When an auxiliary pattern is to be generated with respect to design data, optical proximity correction is applied at step ST1B to design data based on correction information, which includes optical proximity effect correction values indicative of the range affected by optical proximity effect, and defines the rules of optical proximity effect correction. In this manner, corrected design data 13 is derived from the CAD data 10 that is created by the design staff.
At step ST2B, corrected reticle pattern data is generated by converting the corrected design data based on conversion information such as information indicative of a layer in which the pattern is located and sizing information about the size of the pattern. In this manner, corrected reticle pattern data 14 is generated from the corrected design data 13. Image is printed based on the corrected reticle pattern data 14, thereby generating the tangible reticle 15.
The optical proximity correction as described above is not only applied to the real wiring patterns of a semiconductor integrated circuit, but also applied to the dummy patterns.
When a semiconductor integrated circuit is manufactured, generally, significantly different wire densities at different points on the substrate make an optimal etching condition differ from point to point. This gives rise to a problem that the effect of the etching process is not homogeneous. As a result, at places where the wire density is small, resist may disappear to cause breaking of lines, and the width of lines may be narrowed to cause a significant increase in line resistance. In order to avoid such problems and perform etching that can form lines having respective thicknesses with desired precision, a ratio of resist pattern area size to wafer area size needs to be kept to a predetermined ratio. At the place where the size ratio of a wire pattern to a wafer area is small, thus, dummy patterns are inserted so as to achieve an approximately constant size ratio of resist patterns regardless of position on the wafer.
FIG. 2 is an illustrative drawing for explaining a related-art optical proximity correction that is performed when dummy patterns are present.
Mask pattern data 21 includes a main pattern 32 that corresponds to wires and the like and serves as a circuit, and also includes a dummy pattern 31 that is inserted for the purpose of adjusting etching conditions and the like and does not serve as a circuit. The dummy pattern 31 includes a plurality of rectangular patterns arranged to fill an empty area as shown in FIG. 2, for example. Optical proximity correction table information (OPC table information) 22 includes optical proximity effect correction values and the rules of correction pattern generation.
Based on the mask pattern data 21 and the optical proximity correction table information 22, optical proximity correction 23 is performed on the entirety of the mask pattern data 21. In so doing, the main pattern 32 and the dummy pattern 31 are not distinguished from each other, and the same optical proximity correction is applied to all the patterns. As a result, not only the main pattern 32 but also all the rectangular patterns constituting the dummy pattern 31 are corrected as illustrated in mask pattern data 24, which gives an expanded view of a portion of the mask pattern data 21. In this example, smaller rectangular patterns attached to, the corners of each pattern are intended to indicate that this pattern is a corrected pattern having undergone an optical proximity correction.
In this manner, the related-art optical proximity correction not only treats the main pattern corresponding to the portion that serves as a circuit, but also treats all the dummy patterns corresponding to portions that do not serve as a circuit. This gives rise to a problem that optical proximity correction is time-consuming. Further, when a correction pattern is attached to a dummy pattern (i.e., when the dummy pattern is corrected), the size of data that describes the pattern shape increases, which gives rise to a problem that the mask pattern data becomes larger.
Accordingly, there is a need for a method that can efficiently perform optical proximity correction with respect to mask pattern data including dummy patterns.
[Patent Document 1] Japanese Patent Application Publication No. 2001-230250